I checked a walkthrough and it tells me that is the correct path, but it doesnt break!

Could this be a bug?

I took this from the walktrhough

Part 3: Steamrunner

Now you must cross the grids to the other side of the room without being killed by the steam.
Each time the steam blows, some of the grids will remain steam-free.
You can count them and find a safe route to the other side.
Wait for a blowout before one of the center grids will be safe, and immediately after this steam pulse stops, jump onto that grid, wait the next blowout, and jum tp the other side.
After you successfully crossed the grids, move the barrels to uncover the shaft, because the door upstairs is closed.Smash the duct cover and crawl inside.
Take the first route right and go a little way up.
Use another duct to get out. You are now in Shaft 12 that was previously closed.
Move the cart blocking the door, but don't go outside.
Turn around and go down.
Jump onto another cart and use the wire cutters to cut the chains blocking the cart.
Push the cart down. The cart smashes a wall.
Go through that hole.

The text i highlighted is the part were i can´t break the duct!

Any help?

Ps: It´s the second duct, the first blocked by barrels is no problem.
OMFG... i´m dumber than a rock... i don´t need to break it... i just stared at it and saw the icon showing it can be opened...

On one area where a rock comes down after you (a bit like indiana jones) i managed to trick the physics and make the ball stop XD, that´s another problem with the game there, but a positive one since i didn´t get squasehd

There is a small rock you pick, right before that big rock, to cross a little puddle of acid, if you put it in the puddle without releasing it, try to walk to the other side (all this without releasing, you walk on the rock while you grab it) and take the rock with you and drop it where that big rock comes out to get you, it will stop the big rock and it will stay there once it comes out. And if you go and touch it, even though it´s completely still, you get killed XD.